Oscillator circuit arrangement



Nov. 21, 1950 C. J. VAN LOON OSCILLATOR CIRCUIT ARRANGEMENT Filed April6, 1948 3 fig. 1.

T T T I 17 15 d 3 1 ZZZ MRELQMN VANLOON IN V EN TOR.

ATTORNEY Patented Nov. 21, 1950 OSCILLATOR CIRCUIT ARRANGEMENT.

Carel'Jan-"vanliioong Eindhoven, Netherlands, as-

signor t'o Hart-ford National Bank: and 'llrustf- Company; Hartford,Conm, as: trustee.

ApplihationAnril' 6, 1948Serial No. 1912 14 In'the Netherlands April 9,1947 Thei'nvention' relates to oscillator circuit-ar rangem'entsdesigned, more particularly, for superheterod'yne receiving apparat'us'and comprising a positively ba'cl coupled"discharge tube; wherein thefeedback" path extends over a tap on" the inductance coil of" thefrequency determining Eircuit' tunab e by means ofa variable condenser,and a second inductancecoil which is inductively coupled to thefirst-mentioned coil;

The invention has fbrits" object to "minimise in such acircuitarrangementas far aspossible the influence exerted 'bw variationsin temperature on the oscillator frequency;

The" invention will be described with reference to the appended" drawingin which:

' Figure" 1' isa schematic diagram showing one usual form ofoscillator-circuit",

Figure 2- is a schematicdiagram" showing'one form of" circuitarrangement in accordance with the invention,

Figure" 3" is a schematic diagram shcwin'g'another foriri of'ci'rcuit"arrangement in accordance with the invention, and

Figure 4* illustrates the construction" of thefeedbackcoil of thecircuit of Fig: 22'

A usuallyemployed" circuit arrangement is shown inFig: I oft-heaccompanyingdrawing; in which 1- denotes anoscillating discharge tube(-shown hereas a'--triod'e) comprisingacathode 2; agrid 3'-andan anode"4; the latter beingconnected'througha resistance 5 to the positiveterminal of a source of supply currentthe negativetermi'nal of whichmaybeearthed"; The grid connected througlr a grid leakage resistance 6-to the cathode" Zand to"- earth and, moreover, through a condenser F andthe movable arm" of a switch I3 totheupper end of'a coil 8' the 'lowerend ofwhich is-connected to" thecat-hcde. This coil 8 is inductivelycoupled to a-coil 9 which forms part of the frequencydeterminin'g"circuit of the oscillator; which circuitmay be tuned" bymeans of-"a variable" condenser I01 This condenser HI is connected viaamovable arm 14 to the upper end of the coil 9. An invariable a'd'-just'i'ng condenser- H isconnected between the coil 9 and earth, thisseries-connectionbeing connected in=paralle1= with the condenser l0 oneelectrode of which is earthedi The condenser H is a so-ca-lled paddingcondenser which serves toobtain between the tuningirequencyof the"oi'rcuit9; [0 M andthe" tuning frequency of apreceding high frequencycircuit (not shown in the: drawing) a frequency. whichis.-"substantially constant over the-wholerofi the-1 tuningc'range;

Thedesired; feedback betweemthe anode: cit-'- 2 cuit and the gridcircuit 'of' the" tube furthermore takes place through theinvariablecondenser l2 connected between the'annde'. 4 and the upper;endof the coil 9. It" isthuspossible' to produce oscillations thefrequency, of" which is variable by adjustment of .theiposition of thetuning:.condenser l0:

The switch game 1-3 and M are coupled to one another; by' chan ing-overit is; possible to re-, ceive'inan'othenfrequency-range since then thecoilsfl and! and the condenser H are replaced bycoilsvlfiandl'dandacondenser l9 or by coils IT and f8 vand'a condenser;20" respectively; The coils ITand l8 as well" as the coils; l5 and ['6'are coupled to one another: Let us assume, for. ex;- ample; that thecoils 8L1an'd Sandthe condenser- H are in circuit if: it is' desired totune in the short-wave range andl'that the elements l5, l6, I'Q'and'II;l8; 20 serve for the reception in the medium-wave or, long-wave rangerespectively:

This known; circuit-arrangement entails: the disadvantage that,, moreparticularly in shortwave reception; the frequency produced isgreatlydependentupon temperature, which disadvantage naturally is mosttroublesome in the case of apparatus of reduced dimensions whereinduring operationnthe temperature may reach a fairly high value.Thisphenomenon is primarily due to the fact that'the. various straycapacities. of the circuit arran ementvary rather strongly withtemperature. Among these stray capacities" itis more particularly thecapacities in the tube holder; those between the different supply wiresleading to the electrodes of the, tube, the capaciti'es between the liveparts ofthewavelengthswitch and" the. cana itv' between the feedbackcoilandthe tun ng-"coil which are ofimportance.

The influence exert'edby the ca acities of the time holdenby thoseresent in the base of the tube and by the capacitvofTthe wiringmavsubstantia lv be eliminated; or at least greatly reduced, if provision.is made that the feedback pathpasses through a tap, on theiinductance.coil of. the tunablecircuit, for example by connecting the condenser l2of Fig: 1. betweenthe anode 4 and a. tap: on the coil 9-. With thiscircuit-a1.- rangement', even without taking this step, thegrid-cathode: capacity exerts: on the tuning of the circuit 9; til, Honly' a. slight influence since this' 'capacity'is coupled to: the saidcircuit rather loosely and the capacity, reduced to the circuit, is:therefore small. However, owing to the: abovenrentionedi step also theinfluence of the variation in" anOde-cathodecapacityhas=greatlyishedsince the coupling of this capacity to the circuit 9, H), II is greatlyreduced.

If, conversely, the tuned circuit is connected between grid and earth,the influence of a variation in grid-cathode capacity, on the contrary,predominates over the influence exerted by a variation in theanode-cathode capacity on the tuning of the circuit 9, I'll, II. In thiscase the grid 3 must be connected through a coupling condenser to a tapon the coil of the tunable circuit, which results in a great reductionof the influence exerted on the tuning by the gridcathode capacity.

The above-mentioned step consequently permits of greatly reducing theinfluence exerted by a variation in the tube-holder capacity and in anycapacity present in the tube-base, due to variation in temperature, onthe tuning of the circuit 9, l0, H. The said step is, however, far fromeffective since the influence of other capacities likewise highlydependent upon temperature subsists. Moreover, just with the coildestined for the short-wave range the said measure can be carried outwith difficulty only, for in order to obtain a satisfactory oscillatoreffect for all the frequencies of this range it is necessary to couplethe coils through which the inductive coupling takes place,comparatively intensely. It is customary for this purpose to wind thecoil of the tuned circuit, which coil consists for the shortwave rangeof comparatively thick wire, on an insulating core and with a certainintervening space between the turns and to provide the turns of thesecond coil, which consists of thinner wire, between the turns of thefirst-mentioned coil. In this'case it is comparatively diificult toprovide a tap on the said coil of thick wire. Moreover, the capacitybetween these coils is comparatively large and, due to the presence ofthe core of dielectric material, it varies comparatively strongly withtemperature, so that when the apparatus gets warm after beingswitched-on again a rather great frequency shift may be produced.

According to the invention, in order to obviate these disadvantages theinductance coil is divided into two spatially separated parts connectedin series, the junction point of these parts constituting theabove-mentioned tap. These two parts are inductively coupled to thesecond coil which is spatially arranged betwe n the said two parts. Ithas now been found that thus a quite satisfactory back-coupling for theshort-wave range may be obtained and, moreover, that the said frequencyshift is greatly reduced. The tap may be provided in a very easy mannersince the one part of the coil of the tuned circuit. the retroactioncoil and the other part of the coil of the tuned circuit maysuccessively be wound on the same core, whereupon the adjacent ends ofthe said parts are connected to one another, the junction forming theabove-mentioned tap.

One embodiment of the invention is represented in Fig. 2 of theaccompanying drawing, in which elements similar to those of thecircuit-arrangement shown in Fig. 1 are denoted by the same references.For the sake of simplicity the elements serving for the reception in themediumwave and long-wave ranges are omitted.

The circuit-arrangement according to Fig. 2 differs from that accordingto Fig. 1 in that the coil 9 is subdivided into two parts 2| and 22 eachof which is inductively coupled to the feedback coil 8 and whichpreferably are also coupled to one another, the coil 8 being spatiallyarranged between the two parts 2| and 22. The cQnIiQCting wire betweenthe parts 2| and 22, which wire is taken to the outside, is connectedthrough a switch 23 and a condenser 12 to the anode 4, so that in theshort-wave range back-coupling is effected via a tap on the coil of thetunable circuit. The resistance 28 serves to counteract the productionof parasitic oscillations. The switch 23 is coupled with the wavelengthswitches l3 and I4 and is constructed in such manner that in the case ofreception in the mediumor longwave range the anode is connected throughthe condenser 12 to the upper ends of the coils switched into circuit inthe case of reception in these ranges.

Fig. 4 represents a coupling element according to the invention. Thewindings 2i, 8 and 22 are wound on a core 25 of insulating material, thewinding 8 being provided in between the windings 2| and 22. A properchoice of the dimensions of the windings permits to obtain asatisfactory coupling between the winding 8 on the one hand and thewindings 2| and 22 on the other hand, and yet the capacity between thewindings is only small and variation of this capacity due to variationof temperature has therefore only little influence on the tuning of theoscillator circuit. The coil parts 21 and 22 may have, for example, alength of 5 mms. and the coil 8 a length of 2 mms. whilst the diametermay be about 10 mms. and the spacing between the winding 8 and thewinding 2i or 22 may be 1 mm. Each winding may have in this case 8turns. It is evident, however. that other values may also be taken.

With the circuit-arrangement according to Fig. 2 the influence of thestray capacity existing between the conductive parts of the'wave-lengthswitch may still play a comparatively important part. Withcircuit-arrangements according to Figs. 1 and 2 this influence might bereduced by providing the switches l3 and I4 at the lower ends of thecoils instead of at the upper enrs thereof, so that in the case ofreception in the short-wave range the conductive parts are substantiallyat zero potential and variation in the value of the dielectric constantsdue to a variation in temperature no longer influences the tuning of thecircuit 9, I0, I I in this range. Applied to the knowncircuit-arrangement this measure involves, however, difficulties, theprincipal one being that the capacity between the coils 8 and 9 is verytroublesome in the case of reception in the mediumor long-wave range. Incarrying out the present invention this disadvantage does not occursince then the said capacity has a very low value. When carrying out theinvention it is consequently possible Without any objection, in the caseof reception in the mediumor long-wave range, to connect the inductanceto be used for these ranges in series with the inductance 2|, 22 bymeans of the wavelength switch located on that side of the latterinductance which is earthed in the case of reception in the short-waverange, such a circuit-arrangement is shown in Fig. 3.

Elements of the circuit-arrangement according to Fig. 3 which areidentical to those of the circuit-arrangement according to Figs. 1 and 2are denoted by the same references. The circuitarrangement according toFig. 3 differs from that shown in Fig. 2 in that here the wavelengthswitch, which has inter alia two mutually coupled arms 26 and 27, isprovided in such manner that with the reception of frequencies in theshortwave range, when consequently the arms occupy the position shown inFig. 3, it has approximately earth potential owing to the comparativelyhigh, Variation in the.

value of the condenser ll.

capacity between the conductive parts of this other range, for example,to the medium-wave range, a coil I! is connected in series with the coil8 and an inductance l6 and a padding condenser l9 are connected inseries with the parts 2| and 22 of the coil of the tunable oscillatorcircuit. The coils l5 and I6 are coupled to one another in such mannerthat oscillations are generated in the circuit 2|, 22, l6, l9, ID. Thecapacity between the coil 8 on one hand and the parts 2 I, 22 of thecoil of the oscillator circuit on the other hand is low and has noharmful effect. Like in Fig. 1 the mutually coupled coils I! and I8 andthe condenser 20 are switched into circuit in the case of reception inthe long-wave range.

What I claim is:

1. An oscillator circuit arrangement comprising an electron dischargetube having input and output electrodes, resonance circuit meanscomprising a first inductor element and a capacitance element, saidfirst inductor element comprising first and second windings connected inseries and spaced apart, a second inductor element interposed betweensaid first and second windings and inductively coupled thereto, means tocouple one of said electrodes to the junction of said first and secondwindings, and means to couple the other of said electrodes to saidsecond inductor element in feedback relationship.

2. An oscillator circuit arrangement comprising an electron dischargetube having input and output electrodes, resonance circuit meanscomprising a first inductor element and a capacitance element, saidfirst inductor element comprising first and second windings connected inseries and spaced apart, a second inductor element interposed betweensaid first and second windings and inductively coupled thereto, acapacitor interconnecting the said output electrode to the junction ofsaid first and second windings, and means to couple the said inputelectrode to said second inductor element in feedback relationship.

3. An oscillator circuit arrangement comprising an electron dischargetube having input and output electrodes, resonance circuit meanscomprising a capacitance element, a plurality of first inductorsincluding a first inductor element and means to connect said capacitanceelement to said inductors selectively, said first inductor elementcomprising first and second windings connected in series and spacedapart, a plurality of second inductors including a second inductorelement, said second inductor element being interposed between saidfirst and second windings and being inductively coupled thereto, meansto couple one of said electrodes to said first inductors and to thejunction of said first and second windings selectively, and means toselectively coupl the other of said electrodes to said second inductorsin feedback relationship.

4. An oscillator circuit arrangement comprising an electron-dischargetube having input and output electrodes, resonance circuit meanscomprising a first inductor element, and a capacitance element, a secondinductor element, means to connect said second inductor element inseries with said first inductor element and said capacitance element,said first inductor element comprising first,and second windingsconnected in series and spaced apart, a third inductor elementinterposed between said first and second windings and inductivelycoupled thereto, a fourth inductor element inductively coupled to saidsecond inductor element, means to connect said fourth inductor elementin series with said third inductor element, means to couple one of saidelectrodes to the junction of said first and second windings, and meansto couple the other of said electrodes to said third inductor element infeedback relationship.

5. An oscillator circuit arrangement comprising an electron dischargetub having input and output electrodes, resonance circuit meanscomprising a first inductor element and a capacitance element, saidfirst inductor element comprising an insulating core and first andsecond coaxial windings connected in series and spaced apart on saidcore, a second inductor element coaxially wound on said core andinterposed between said first and second windings and inductivelycoupled thereto, means to couple one of said electrodes to the junctionof said first and second windings, and means to couple the other of saidelectrodes to said second inductor element in feedback relationship.

CAREL JAN VAN LOON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,931,338 Wheeler Oct. 17, 19332,036,319 Case Apr, 1'7, 1936 FOREIGN PATENTS Number Country Date559,477 France June 15, 1923 Certificate of Correction Patent No.2,531,312 November 21, 1950 GAREL- JAN VAN LOON Itis hereby certifiedthat error appears in the printed specification of the above numberedpatent requiring correction as follows:

Column 1, line 53, before the Word frequency insert deference;

and that the said Letters Patent should be read as corrected above, sothat the same may conform to the record of the case in the PatentOffice. Signed and sealed this 30th day of January, A. D. 1951.

THOMAS F.- MURPHY,

Assistant Oommz'ssz'oner of Patents.

